Os not found message appearing on the screen

Issue – After upgrading a server to Windows 2003 Enterprise Edition and adding additional memory, the OS still shows only 4 GB of RAM.

Additional Information – Physical Address Extension (PAE)

In Windows Server 2003, PAE is automatically enabled only if the server is using hot-add memory devices. In this case, you do not have to use the /PAE switch on a system that is configured to use hot-add memory devices. In all other cases, you must use the /PAE switch in the Boot.ini file to take advantage of memory over 4GB.

The newer Dell servers are capable of using hot-add memory devices, but the older servers do not.

If you upgrade an older Dell server and are experiencing the issue above, make the following change to the boot.ini file.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)WINDOWS="Windows Server 2003, Enterprise" /fastdetect /PAE

Add the /PAE flag to the end of the boot device. Then reboot the server.

After rebooting the correct amount of memory should be displayed

To summarize, PAE is a function of the Windows 2000 and Windows Server 2003 memory managers that provides more physical memory to a program that requests memory. The program is not aware that any of the memory that it uses resides in the range greater than 4 GB, just as a program is not aware that the memory it has requested is actually in the page file.